Abstract:

1. Nutrition plays an important role in physiological stress resistance and by adjusting their
intake of key nutrients, such as protein and carbohydrate, many animals can better resist stress.
2. Poor nutrition may contribute to the widespread and on-going declines of honeybee populations
by increasing their vulnerability to abiotic (e.g. pesticides) and biotic (e.g. diseases) stressors. However,
we do not know how nutrition affects stress resistance in social insects such as honeybees.
3. Here, we examined how exposure to the toxic secondary metabolite nicotine, a neurotoxin
that shares structural similarities with the neonicotinoid pesticides, and low temperatures
affected nutrient regulation in honeybees using the Geometric Framework of nutrition.
4. Groups of queenless, newly emerged worker bees were given diets containing specific ratios
of protein and carbohydrate to determine, first, how toxin exposure and ambient temperature
affected their nutrient intake and, secondly, how nutrition affected survival under stress.
5. We find that low temperatures and nicotine interacted to reduce survival in African honeybees
that ate low protein, high carbohydrate diets. However, bees fed a high protein diet were
better able to survive insult with these interacting stressors.
6. Although protein conferred a survival benefit in honeybees exposed to these dual stressors,
when allowed to self-select their diet, caged workers did not shift their intake towards a higher
protein food to improve their survival under these stressful conditions.
7. We discuss the possible constraints on nutrient regulation in honeybees and the role that
diet could play in their decline.